Here are a few photos of some kids in my complex playing volleyball, Could you guys tell me what i could have done to make these photos more clear and sharp ?and maybe better color ? my settings were:
1/1000 - F/8 - Vivid - ISO 200-250 18-105mm i hope i got that right

Your pics look plenty sharp and clear to me. If anything, because the background is on the busy side, I would've tried to gain some separation by opening up the aperture and/or zooming. e.g. 100mm, f2.0:

Shutter speed seemed fine. Although, I personally would've gone slower in order to capture just a little motion blur--e.g. I used 1/250 in the pic I posted--because I feel it imparts a sense of... well... motion, and so gives the image an action feel. But that's completely a matter of personal preference. And yes, to keep exposure constant, a larger aperture will mean a lower ISO (or an ND filter).

But I don't think f5.6 will make much difference "bokeh" wise. Using just the kit lens, you could try zooming less, but even at the short end, f3.5(?) may not be wide enough. So you may just have to re-frame the shot so the background is less distracting. If you want to make any changes at all, that is, like I said, the pics look fine to me as they are.

Or, if you have $150 burning a hole in your pocket, I believe Nikon has a 50mm f1.8 that can do some nice bokeh. Of course, in broad daylight, even at ISO100, in order to shoot wide open (f1.8), you're also going to need an ND filter.